Gareth Williams was a Welsh mathematician and employee of GCHQ, seconded to the Secret Intelligence Service (SIS or MI6) who was found dead in suspicious circumstances at a Security Service safe house flat in Pimlico, London, on 23th August 2010.
Police visited Gareth Williams's home during the afternoon of Monday 23th August 2010, as a "welfare check" after colleagues noted he had been out of contact for several days. His naked, decomposing remains were found in the bath of the main bedroom's en-suite bathroom, inside a red bag that was padlocked from the outside. Williams's date of death was estimated to have been the 16th August, one week before he was found.